A PQ is a performance qualification which is conducted prior to a system becoming operational. The PQ tests the system to ensure it meets its operational objectives in a real world operational environment. It is the final step in equipment and systems qualification. A PQ should never be a re-execution of the vendor supplied Operational Qualification (OQ). The OQ should have tested all the operational critical attributes of the system and these tests should be traced back to the SYSTEMS User Requirement Specification (URS).